The product key is a usually unique, alphanumeric code of any length required by many software programs during installation.
They help software developers ensure that each copy of their software was legally purchased.
Most software, including some operating systems and programs from the most popular software makers, require product keys.
As a general rule these days, if you pay for a program, then it probably requires a product key during installation.
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In addition to product keys, some software makers, including Microsoft, often require product activation to help further ensure that software is obtained legally.
Open-source and free software programs usually don’t require a product key unless the manufacturer implements its use for statistical purposes.
Product keys are also sometimes called CD keys, key codes, licenses, software keys, product codes, or installation keys.
How Product Keys Are Used
A product key is like a password for a program.
This password is given upon buying the software and can only be used with that specific application.
Without the product key, the program will most likely not open past the product key page, or it might run but only as a trial of the full version.
Product keys can usually only be used by one installation of the program
but some product key servers allow for the same key to be used by any number of people so long as they’re not used simultaneously.
In these circumstances, there’s a limited number of product key slots, so if the program using the key is shut down, another can be opened and use that same slot.
Microsoft Product Keys
All Microsoft Windows operating system versions require the entry of unique product keys during the installation process, as do all versions of Microsoft Office and most other Microsoft retail programs.
Microsoft product keys are often located on a product key sticker.
In most versions of Windows and other Microsoft software, product keys are 25 characters in length and contain both letters and numbers.